19 states are at risk of compounding their fiscal difficulties because of a somewhat obscure feature of their income tax codes known as the net operating loss (NOL) "carryback" deduction. This provision allows businesses to file amended income tax returns for past years in which they were profitable, use current year business losses to offset those profits, and receive refunds of taxes paid in past years. During recessions, when tax payments by businesses tend to fall in any case, refunding business taxes paid in prior years can make revenue shortfalls even larger. These 19 states could avoid some loss of personal and/or corporate income tax revenue during the current fiscal crisis — and future recessions — if they act now to disallow NOL carrybacks.